1. Technical Field
The present invention relates in general to digital communications and in particular to methods for defining the structure of a document within a data stream. Still more particularly, the present invention relates to methods for defining relationships between document elements utilized in both logical and layout document definitions.
2. Background Art
Text processing applications are well known in the prior art. Such applications typically utilize data streams which include embedded formatting and textual commands. These commands generally vary from one application program to another. Revisable Format Text Document Content Architecture (RFTDCA) was developed to provide for the interchange of data streams from different text processing applications and to allow for the consistent interpretation of embedded formatting and textual commands.
The International Standards Organization (ISO) has defined standards for document processing and interchange. Specifically, the Standard Generalized Markup Language (SGML), publication 8879, and Office Document Architecture/Office Document Interchange Facility (ODA/ODIF), publication 8613, are two such standards. SGML is a syntax language represented by character text and may be utilized to define the specifications for publishing systems. Generic markup, that is, identification of the role of document elements rather than how to present those elements, is the basis of SGML.
In current architectures, such as SGML, the definition of a structure of a document includes expressions which define the relationships of document elements utilizing special characters which have assigned meanings relating to element relationships. In addition, the type of expression (i.e. Document Content; Attribute etc.) is directly associated with the expression itself. Thus, known architectures require replicated specifications for like parameters.
Additionally, known architectures generally require adherence to strict punctuation requirements and positional semantics wherein variations in the position of a character may have a substantial effect on the resultant semantics.